FIG. 1 depicts an air-bearing surface (ABS) view of a conventional read transducer 10. The conventional read transducer 10 includes shields 12 and 20, sensor 14 and magnetic bias structures 19. The read sensor 14 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor. The read sensor 14 includes an antiferromagnetic (AFM) layer 18, a pinned layer 17, a nonmagnetic spacer layer 16, and a free layer 15. Also shown is a capping layer. In addition, seed layer(s) may be used. The free layer 15 has a magnetization sensitive to an external magnetic field. Thus, the free layer 15 functions as a sensor layer for the magnetoresistive sensor 14. These magnetic bias structures 19 are used to magnetically bias the free layer 15 of the sensor 14.
The conventional free layer 15 consist of a CoFe/CoB bilayer (not separately depicted in FIG. 1). The CoB in the bilayer may aid in obtaining a higher moment and lower magnetostriction in the free layer 15 than would be obtained for NiFe in the free layer 15. The CoB is amorphous as-deposited, which aids in preventing an MgO barrier layer 16 and the free layer 15 from crystalizing in an orientation other than the desired (100) orientation. This is in contrast to other materials such as NiFe which may crystallize the free layer 15 in FCC (111) orientation. Thus, the CoFe/CoB bilayer is desired to be used in the conventional free layer 15.
Although conventional free layers 15 may be desired to include a CoFe/CoB bilayer for the above reasons, such a conventional sensor 14 may be more prone to corrosion during fabrication. The free layer 15 may also be subject to residual stress. Residual stress may be induced during the deposition and post anneal of the CoB portion of the free layer 15, as well as in the following processing. A sufficiently high residual stress might cause the free layer 15 to peel off of the device 10 or to crack. In addition, the electron corrosion potential for the sensor 14 in various developers may significantly influence film corrosion resistance. The CoFe/CoB bilayer may have a high electron corrosion potential for preferred developers. Thus, the sensor 14 is more likely to corrode during fabrication. Improvements in the fabrication and design of the free layer 15 are desired to extend the magnetic transducer 10 to higher densities.
Accordingly, what is needed is a system and method for improving the performance of a magnetic recording read transducer.